The book is like anything else. It isn't so much what exercises you do, but HOW you do them. Some teachers and students are more accustomed to musical exercises. They may find the work a bit harsh. Others really take well to abstract exercises. Here is a book that will never be finished.
No matter what a book claims to do or be, it is my opinion that it is what worked for the teacher that wrote it, perhaps it is what worked with their students, or with themselves as students. Like many other books, I found some really nice exercises that I found to be useful. I did not find following the strict routine outline to be useful. I don't have that kind of time, and I think there are more beneficial ways to spend that time. However, what I DID find VERY useful was the idea of routines in general. I loved the idea behind the routines. Organized practice. Some exercises do this. Some do that. Others do different things. Everyday, I need a little of this, a little of that, and some of that. And, I think it is very beneficial to not have the same routines, not unlike mixing it up when you go to the gym. Iznaola really got be thinking about that in a very important way. As a result, I think my practice time (and my practice log) is far more organised.
I think taking a close look at the book is worth the time for a serious student. You may find new exercises that you find useful. And whether you really work much out of the book or not, it may significantly change the way you think about organizing your practice with Berg, Shearer, Yates, whatever. Whether it was Iznaola's intent or not, the most valuable thing I got from the book was better organisation. And ironically, that usually means far less time in the practice chair than what Kitharologus might imply.
Dr. Todd Tipton, classical guitarist
Cincinnati, OH, USA (available via Skype)